1. Field of the Invention
The present invention relates to laser-related uses of diamond. More particularly, the present invention relates to laser-related uses of single-crystal diamond produced using Microwave Plasma Chemical Vapor Deposition (MPCVD) within a deposition chamber.
2. Description of Related Art
Diamond, in addition to its gem properties, is the hardest known material, has the highest known thermal conductivity, and is transparent to a wide variety of electromagnetic radiation. Diamond, with its high Raman frequency shift (Δν=1332.5 cm−1) combined with very high Raman gain coefficient (g>15 cm·GW−1) [G. A. Pasmanik, Laser Focus World 35, 137 (1999)], is also one of most interesting crystals for stimulated Raman scattering (SRS) generation. Monocrystalline (or single crystal) diamond in particular possess a wide range of important properties, including a low coefficient of thermal expansion, the highest known thermal conductivity, chemical inertness, wear resistance, low friction, and optical transparency from the ultra-violet (UV) to the far infrared (IR). Therefore, it is valuable because of its wide range of applications in a number of industries and research applications, in addition to its value as a gemstone.
For at least the last twenty years, a process of producing small quantities of diamond by chemical vapor deposition (CVD) has been available. As reported by B. V. Spitsyn et al. in “Vapor Growth of Diamond on Diamond and Other Surfaces”, Journal of Crystal Growth, vol. 52, pp. 219-226, the process involves CVD of diamond on a substrate by using a combination of methane, or another simple hydrocarbon gas, and hydrogen gas at reduced pressures and temperatures of 800-1200° C. The inclusion of hydrogen gas prevents the formation of graphite as the diamond nucleates and grows. Growth rates of up to 1 μm/hour have been reported with this technique.
Subsequent work, for example, that of Kamo et al. as reported in “Diamond Synthesis from Gas Phase in Microwave Plasma”, Journal of Crystal Growth, vol. 62, pp. 642-644, demonstrated the use of Microwave Plasma Chemical Vapor Deposition (MPCVD) to produce diamond at pressures of 1-8 kPa at temperatures of 800-1000° C. with microwave power of 300-700 W at a frequency of 2.45 GHz. A concentration of 1-3% methane gas was used in the process of Kamo et al. Maximum growth rates of 3 μm/hour have been reported using this MPCVD process. In the above-described processes, and in a number of other reported processes, the growth rates are limited to only a few micrometers per hour.
Recent efforts, however, have increased the growth rate, quality and size of the diamonds grown in an MPCVD process.
U.S. Pat. No. 6,858,078 to Hemley et al., which is hereby incorporated in its entirety by reference, is directed to an apparatus and method for diamond production.
U.S. application Ser. No. 11/438,260, filed May 23, 2006, which is hereby incorporated in its entirety by reference, is directed to producing colorless, single-crystal diamonds at rapid growth rate using Microwave Plasma Chemical Vapor Deposition (MPCVD) within a deposition chamber.
U.S. application Ser. No. 11/599,361, filed on Nov. 15, 2006, which is hereby incorporated in its entirety by reference, is directed to new uses for colorless, single-crystal diamonds produced at a rapid growth rate. The application is also directed to methods for producing single crystal diamonds of varying color at a rapid growth rate and new uses for such single-crystal, colored diamonds.
Until now, relatively few attempts have been made to use single-crystal diamond as a laser component.
U.S. Pat. No. 5,420,879, issued May 30, 1995, is directed to a solid state laser which includes synthetic diamond crystal as a medium of laser beam emission and generates a laser beam having a wavelength of 225 to 300 nm. The synthetic diamond crystal used in the invention is produced via a high pressure method, not by chemical vapor deposition.
U.S. Pat. No. 6,667,999, issued on Dec. 23, 2003, discloses a method and apparatus for cooling a high power laser oscillator or amplifier using diamond as an optically transparent heat transfer medium. The patent does not disclose the use of single crystal CVD diamond as a heat transfer medium.
U.S. Pat. No. 6,574,255, issued on Jun. 3, 2003, discloses external cavity optically-pumped semiconductor lasers that can include single crystal CVD diamond, but as a film.
Thus, there remains a need to develop new laser-based uses for single-crystal CVD diamonds.